Surface Epitaxial Growth of 2D/2D Bi₂O₂S/CdS Heterojunction Photoanodes and Their Photoelectrochemical Properties

Constructing high catalytic activity heterojunctions to compensate for the shortcomings of single catalysts has promoted the development of semiconductor catalysts in photoelectrochemical (PEC) water splitting. In this case, the 2D/2D Bi₂O₂S/CdS composite was successfully constructed by an in situ surface epitaxial growth method. At 1.23 V vs RHE, the catalytic activity of Bi₂O₂S/CdS with a 2D/2D heterojunction is the highest, and the current density of the Bi₂O₂S/CdS photoanode is 3.46 mA/cm². Compared with the Bi₂O₂S photoanode (0.59 mA/cm²), the performance has been improved by 5.86 times. In electrochemical impedance spectroscopy testing, the arc radius of 2D/2D Bi₂O₂S/CdS is smaller than that of Bi₂O₂S, indicating faster charge-transfer kinetics. The data show that the 2D/2D heterojunction with surface-surface contact successfully enhances the catalytic activity of Bi₂O₂S, greatly elevating the efficiency of charge separation and migration. This study provides a method to enhance the PEC activity in type-I heterojunction photoelectrodes, promoting the application of Bi₂O₂S-based materials in photoelectrochemistry.